Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$114.77	13.118%	$129.8255	$129.83	$129.85	$129.80
Purchase #2	$94.95	11.242%	$105.6243	$105.62	$105.60	$105.60
Purchase #3	$156.73	11.327%	$174.4828	$174.48	$174.50	$174.50
Purchase #4	$174.59	10.380%	$192.7124	$192.71	$192.70	$192.70
Purchase #5	$29.85	9.247%	$32.6102	$32.61	$32.60	$32.60
Purchase #6	$36.64	3.481%	$37.9154	$37.92	$37.90	$37.90
Purchase #7	$86.34	10.652%	$95.5369	$95.54	$95.55	$95.50
7 purchase totals =	$693.87		$768.7075	$768.71	$768.70	$768.60